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International migration vs. co-authorship RelationshipDefinitionComment International co-authorship Authors from institutions located in different countries jointly publish a paper Country relates to where authors work, NOT to their nationality International migration A scientific author moves from one country to another

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The model - 1 Theoretical concept; Interpretation Bibliometric construct / feature ResearcherAuthor id Research active (in a year)Publishing (in a year) Currently activePublishing in 2011 Starting a scientific career during years T1-T2 First publication during T1-T2 Young in 2011First publication year > 2000 Moving from country A to BPublishing authors work country changes consecutively from A to B Transients are deleted

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Author profiling in Scopus Assigns to each author a unique number Groups each authors documents....... based on similarity in affiliation, publication history, subject and co-authors Aims at high precision ( lower recall) New algorithm implemented in April 2011 Author feedback system in place

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Study set: authors starting their career in a study country Question: How many moved abroad, how many returned?

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Study set: Young authors starting their career in a study country Question: How many move abroad, how many return? Post Docs returning to their home country? Post-Docs not returning to their country? Or PhD students returning after attaining their PhD?

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Case study: Data sample analysed 100 author-ids in chemistry randomly selected from Scopus Search for other author-ids that relate to the same authors as those represented in the sample Precision of the 100 author-ids themselves was not examined Emphasis on recall rather than precision

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Findings – 1 27% of the researchers did have additional author ID's For the 27 % researchers that did have additional ID's, in total 51 additional author IDs were found Half of the additional author IDs had 1 paper only; and 75 % at most 2

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Implications for the migration study HomonymsSynonyms Definition/ Examples One author id relates to different persons (common names) A researcher has more than one author id (split identities) TendenciesThe more common a name, the larger the number of articles Second identity for author ids with few articles only (typically 1-3) In analysisNewcomers as from 2001 Transients are not taken into account